#include // this function prototype is a declaration of sumTo int sumTo(int); int main(int argc, char **argv) { printf("sumTo(5) is: %d\n", sumTo(5)); return 0; } // sum integers from 1 to max int sumTo(int max) { int i, sum = 0; for (i=1; i<=max; i++) { sum += i; } return sum; }